zfs discuss - Feb 2009 - Bad sectors arises -> discs differ in size -> trouble?

You have a raid with 5 terabyte discs. Now some bad sectors arises, so the discs
differ in size. What happens with the ZFS raid? Will there be seriuos trouble?
Or is this only a problem when ZFS raid is 100% full?

Of old, in Linux you didnt allocate the entire disc. Instead you let 100MB be
free so there would be headroom for bad sectors. If there are bad sectors the
discs will differ in size. Is this a problem?
-- 
This message posted from opensolaris.org

On Sun, Feb  1 at 14:45, Orvar Korvar wrote:
> You have a raid with 5 terabyte discs. Now some bad sectors arises,
> so the discs differ in size. What happens with the ZFS raid? Will
> there be seriuos trouble? Or is this only a problem when ZFS raid is
> 100% full?
>
> Of old, in Linux you didnt allocate the entire disc. Instead you let
> 100MB be free so there would be headroom for bad sectors. If there
> are bad sectors the discs will differ in size. Is this a problem?
>
Disk vendors already maintain enough spare capacity so that the drive
can transparently provide defect management for a few hundred thousand
bad sectors without having to report that it''s smaller.

If the device reports a smaller capacity than sold originally, short
of things like HPA or DCO, it has likely exhausted its spare pool, and
it''s time to RMA the drive with some urgency.

-- 
Eric D. Mudama
edmudama at mail.bounceswoosh.org

Ok. Just to confirm: A modern disk has already some spare capacity which is not
normally utilized by ZFS, UFS, etc. If the spare capacity is finished, then the
disc should be replaced.
-- 
This message posted from opensolaris.org

Orvar Korvar wrote:
> Ok. Just to confirm: A modern disk has already some spare capacity which is
not normally utilized by ZFS, UFS, etc. If the spare capacity is finished, then
the disc should be replaced.
>   
Yup, that is the case.

Ok thanks for your help guys! :o)

One last question, how do I know that the spare sectors are finishing? SMARTS
are not available for Solaris, right? Is there any warnings that plop up in ZFS?
Will scrubbing reveal that there are errors? How will I know?
-- 
This message posted from opensolaris.org

On Mon, Feb  2 at  5:05, Orvar Korvar wrote:
> Ok. Just to confirm: A modern disk has already some spare capacity
> which is not normally utilized by ZFS, UFS, etc. If the spare
> capacity is finished, then the disc should be replaced.
Actually, the device has spare sectors beyond the reported LBA
capacity.  These are transparently exchanged with sectors within the
LBA capacity when those sectors develop permanent errors.

Filesystems often leave reserve areas, but that is unrelated.

--eric

-- 
Eric D. Mudama
edmudama at mail.bounceswoosh.org

On Mon, Feb  2 at  5:48, Orvar Korvar wrote:
> Ok thanks for your help guys! :o)
>
> One last question, how do I know that the spare sectors are
> finishing? SMARTS are not available for Solaris, right? Is there any
> warnings that plop up in ZFS? Will scrubbing reveal that there are
> errors? How will I know?
Short of SMART, I am not sure.  If SMART isn''t supported, someone
should port support for it.

-- 
Eric D. Mudama
edmudama at mail.bounceswoosh.org

Hi

Eric D. Mudama schrieb:
> Short of SMART, I am not sure.  If SMART isn''t supported, someone
> should port support for it.
> 
I''m not sure if Sun''s hd tool is working everywhere of if it
specific to
certain machines:

hd -e c5t6
Revision: 16
Offline status 130
Selftest status 0
Seconds to collect 10419
Time in minutes to run short selftest 1
Time in minutes to run extended selftest 174
Offline capability 91
SMART capability 3
Error logging capability 1
Checksum 0x16
Identification                     Status Current Worst         Raw data
  1 Raw read error rate            0xb        100   100                0
  2 Throughput performance         0x5        159   159              206
  3 Spin up time                   0x7        108   108      55876649604
  4 Start/Stop count               0x12       100   100               64
  5 Reallocated sector count       0x33       100   100                0
  7 Seek error rate                0xb        100   100                0
  8 Seek time performance          0x5        136   136               31
  9 Power on hours count           0x12        99    99             7607
 10 Spin retry count               0x13       100   100                0
 12 Device power cycle count       0x32       100   100               64
192 Power off retract count        0x32       100   100              256
193 Load cycle count               0x12       100   100              256
194 Temperature                    0x2        183   183  30/ 16/ 42
(degrees C cur/min/max)
196 Reallocation event count       0x32       100   100                0
197 Current pending sector count   0x22       100   100                0
198 Scan uncorrected sector count  0x8        100   100                0
199 Ultra DMA CRC error count      0xa        200   253                0

Does this help?

Cheers

Carsten

Orvar Korvar wrote:
> Ok. Just to confirm: A modern disk has already some spare capacity which is
not normally utilized by ZFS, UFS, etc. If the spare capacity is finished, then
the disc should be replaced.
>   
Also, if ZFS decides that a block is bad, it can leave it unused.
For example, if you have a mirrored pool, it is not required that
block N on vdev1 == block N on vdev2. In a sense, this works
like block sparing.

Regarding SMART, there is much discussion on this in the
archives. In a nutshell, there are FMA modules which use
SMART data. There are a few tools which allow an administrator
to see SMART data. Some question whether SMART data is
actually useful.
-- richard

Hello Richard,

Monday, February 2, 2009, 5:39:34 PM, you wrote:

RE> Orvar Korvar wrote:
>> Ok. Just to confirm: A modern disk has already some spare capacity
which is not normally utilized by ZFS, UFS, etc. If the spare capacity is
finished, then the disc should be replaced.
>>   
RE> Also, if ZFS decides that a block is bad, it can leave it unused.
RE> For example, if you have a mirrored pool, it is not required that
RE> block N on vdev1 == block N on vdev2. In a sense, this works
RE> like block sparing.

Would ZFS mark such a block permanently as bad? Under what
circumstances?

-- 
Best regards,
 Robert Milkowski
                                       http://milek.blogspot.com